The design and operation of a simple transient digitizer are described, capable of digitizing repetitive analog–transient signals with 30 ns, 8 bit resolution, at repetition rates of at least 300 Hz. The 2 μs maximum transient width (64 samples at 30 ns intervals per transient) can easily be extended. The digitizer connects directly to a single 8-bit TTL-compatible microcomputer I/O port. The circuit uses only commercially available integrated circuits, and the total parts cost is low. Both circuitry and software are described.